Early steep decay from high latitude emission in the internal shock framework. Two examples of synthetic GRBs with a smooth (dashed line) or a highly variable (solid line) light curve. Top left: initial distribution of the Lorentz factor in the flow as a function of injection time t_inj (a short timescale (0.5 s) fluctuation of the Lorentz factor is added to produce the variable burst). In the two cases, the injected kinetic power is constant. Top right: shock radius (smooth light curve case: thick line; variable light curve case: thin line) as a function of observer time, showing that the maximum values reached by the emission radius, i.e. R_γ, are comparable in the two cases. Bottom: bolometric light curve on either a linear (left panel) or logarithmic (right panel) scale. The high latitude contribution is very similar for both the smooth and variable light curves.